J. Zhang, et al.
CatalysisTodayxxx(xxxx)xxx–xxx
and composition. Aluminosilicate and gallosilicate forms of zeolite
MTW in bulk and hierarchical “nanosponge” form were tested in the
acylation of toluene with benzoyl chloride. Also, conventional zeolites
*BEA and MFI were tested for reference purposes.
2.2. Characterization
The structure and crystallinity of the zeolites were determined by X-
ray powder diffraction using a Bruker AXS D8 Advance diffractometer
equipped with a graphite monochromator and a position sensitive de-
tector LYNXEYE XE-T using CuKα radiation in Bragg–Brentano geo-
metry.
2. Experimental section
Argon adsorption/desorption isotherms were measured on
a
2.1. Synthesis of zeolites
Micromeritics 3Flex volumetric Surface Area Analyser at 87 K to de-
termine surface area, pore volume and pore size distribution. Before the
sorption measurements, all samples were degassed in a Micromeritics
Smart Vac Prep instrument under vacuum at 250 °C (heating rate 1 °C/
min) for 8 h. The specific surface area was evaluated by BET method
using adsorption data in the range of a relative pressure from p/
p0 = 0.05 to p/p0 = 0.25. The DFT method was applied to determine
the volume of micropores (Vmic). The adsorbed amount at relative
pressure p/p0 = 0.98 reflects the total adsorption capacity (Vtot). The
pore size distributions were calculated using the BJH model from the
desorption branch of the isotherms.
TEM imaging was performed using JEOL NEOARM 200 F with a
Schottky-type field emission gun at accelerating voltage of 200 kV.
Microscope was equipped with TVIPS XF416 CMOS camera. The
alignment was performed using standard gold nanoparticles film
method. Due to low beam-stability of the sample the dose of electrons
was kept below current density of 2 pA/cm2.
2.1.1. Synthesis of SDAs
The synthesis of the nanosponge zeolites utilizes specially designed
structure directing agents (“SDAs”), further denoted as „C22N6“. The
preparation of C22N6 was performed by reaction of 1-bromodocosane
with six times molar excess of N,N,N’,N’-tetramethyl-1,6-diamino-
hexane in a mixture of toluene and acetonitrile (volume ratio 1:1; 25 ml
per 1 g of 1-bromodocosane at 60 °C for 12 h. The solvents were eva-
porated and the product was washed with diethyl ether and dried at
room temperature. Subsequently, the precursor is mixed with ten times
molar excess of 1,4-bis(chloromethyl)benzene in a mixture of chloro-
form and acetonitrile volume ratio 2:1; 36 ml per 1 g of the precursor).
The reaction was carried out at 65 °C for 24 h. Following, the solvents
were evaporated, the product thoroughly washed with diethyl ether
and acetone and then dried at room temperature. The product was
mixed with half its molar amount of N,N,N’,N’-tetramethyl-1,6-diami-
nohexaneand dissolved in chloroform (6.3 ml per 1 g). The reaction was
carried out at 85 °C for 24 h. Lastly, the chloroform was evaporated, the
product was washed with diethyl ether and dried at room temperature.
The purity of the final product was checked with 1H NMR spectroscopy.
The concentration and type of acid sites were determined by ad-
sorption of pyridine as a probe molecule and observed by FTIR spec-
troscope Nicolet 6700 AEM equipped with DTGS detector, using the
self-supported wafer technique. Prior to adsorption of the probe mole-
cule, self-supported wafers of zeolite samples were activated in-situ by
overnight evacuation at temperature 450 °C. Pyridine adsorption pro-
ceeded at 150 °C for 20 min at partial pressure 3 Torr, followed by
20 min evacuation at 150 °C or 450 °C. The concentrations of Brønsted
and Lewis acid sites in aluminosilicate samples were calculated from
integral intensities of individual bands characteristic of pyridine on
Brønsted acid sites at 1545 cm–1 and band of pyridine on Lewis acid site
2.1.2. Hydrothermal synthesis
The synthesis of aluminosilicate bulk MTW zeolite was carried out
using tetraethylammonium hydroxide as SDA. Sodium aluminate was
dissolved in distilled water and then TEA–OH was added. Colloidal si-
lica (Ludox HS-40) was diluted to 30% with distilled water in a separate
vessel. Both solutions were mixed together and homogenized by stir-
at
ε(B) = 1.67
1455 cm–1
and
molar
absorption
coefficients
of
re-
ring. The final molar composition of the gel was 100 SiO2 : 1 Al2O3
:
0.1 cm.μmol–1 and ε(L) = 2.22
0.1 cm.μmol–1
,
1.46 Na2O : 25 SDA : 1330 H2O. The crystallization was carried out in a
Teflon-lined steel autoclave at 160 °C for 6 days under static conditions.
The product was recovered by filtration, washed with distilled water,
dried at 65 °C and subsequently calcined in a flow of air at 550 °C for
6 h. Gallosilicate bulk MTW was prepared using the same procedure
replacing the sodium aluminate with gallium nitrate. Additional so-
dium hydroxide was added to compensate for the sodium ions in so-
dium aluminate in order to keep the same molar composition of the
mixture. The calcination of gallosilicate bulk MTW was carried out in a
flow of air at 250 °C for 6 h followed by 450 °C for 2 h.
spectively. The spectra were recorded with a resolution of 4 cm−1 by
collection 128 scans for single spectrum.
The purity of prepared organic SDAs was verified by measuring 1H
NMR spectra on a Varian Mercury 300 MHz spectrometer. D4 methanol
was used as the solvent.
2.3. Acylation of P-xylene
The catalytic tests were performed in the liquid phase under at-
Aluminosilicate nanosponge MTW zeolite was prepared using the
C22N6 as SDA. Sodium aluminate and sodium hydroxide were dis-
solved in water and the mixture was heated up to 60 °C. The SDA was
added and when completely dissolved it was left to cool down to room
temperature. The mixture was transferred to a polypropylene bottle,
tetraethylorthosilicate was added and the whole bottle was shaken. The
aging was carried out at 60 °C for 20 h. The final molar composition of
the gel was 100 SiO2 : 1 Al2O3 : 13 Na2O : 3.333 SDA : 4500 H2O. The
crystallization was carried out in a Teflon-lined steel autoclave at
150 °C for 6 days with rotation. The product was recovered by filtration,
washed with distilled water and dried at 65 °C. The calcination was
carried out under a flow of air at 580 °C for 8 h. Gallosilicate nanos-
ponge MTW was prepared using the C22N6 as SDA following the same
procedure. Sodium aluminate was replaced by gallium nitrate and ad-
ditional sodium hydroxide was added to compensate for the sodium
ions.
mospheric pressure at 130 °C in a multi-experiment workstation
StarFish. Prior to the experiment, 50 mg of the catalyst was activated at
450 °C for 90 min with a rate of 10 °C/min. Then 5 ml of p-xylene,
0.25 g of n-dodecane and the catalyst (for a blank experiment the cat-
alyst was not used) were placed in a three-necked vessel equipped with
a condenser and a thermometer and heated to the reaction temperature.
When the desired temperature was achieved, 5 mmol of benzoyl
chloride were added into the vessel to start the reaction. Then, samples
of the reaction mixture were taken in 0 min, 10 min, 30 min, 1 h, 2 h,
3 h, 4 h, and 5 h. When the sample was taken it was centrifuged to re-
move the catalyst and remaining solution was analysed by gas chro-
matography. Gas chromatograph Agilent 7890B GC equipped with HP-
5
column (length 30 m, diameter 0.320 mm, and film thickness
0.25 μm) and flame ionization detector was used for the analysis.
Commercial zeolites were purchased from Zeolyst International:
*BEA (CP814E, Si/Al = 12.5) and MFI (CBV 3024E, Si/Al = 15).
2